The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 10-280165 filed Oct. 1, 1998.
1. Field of the Invention
The present invention relates to a polarizing device and a projector More specifically, it relates to a polarizing device which is utilized when performing a polarization splitting on light fluxes corresponding to a plurality of colors resulting from a color separation performed on light emitted from a light source, guiding the light fluxes having undergone polarization splitting to a plurality of light valves and analyzing the light fluxes corresponding to the plurality of colors that have been modulated at the individual light valves, and a projector that composes (synthesizes) the light fluxes analyzed by using the polarizing device at a color composition optical system and projects the composed light on a screen via a projection lens.
2. Description of the Related Art
Projectors employed to project an image onto a screen in the known art include the projector disclosed in Japanese Patent Publication No. 2599309. To explain this projector in reference to FIG. 7, light source light emitted from a light source 61 undergoes color separation at dichroic mirrors 62 and 63 and thus becomes separated into R light, G light and B light which are then guided to polarization beam splitters 64R, 64G and 64B provided in correspondence to the different color light. Only the polarization split light in the light guided to the polarization beam splitters 64R, 64G and 64B is guided to reflection type light valves 65R, 65G and 65B. The light having entered the light valves 65R, 65G and 65B are modulated in correspondence to color signals input to the individual light valves when they are reflected at the light valves 65R, 65G and 65B. The light having been modulated and reflected at the light valves 65R, 65G and 65B are respectively guided to the polarization beam splitters 64R, 64G and 64B and only the modulated light are analyzed at the polarization beam splitters 64R, 64G and 64B and extracted. The analyzed light fluxes are then color-composed at a cross-dichroic prism 66 and a full color projected image is projected onto a screen (not shown) by a projection lens 67.
To explain the different color light fluxes obtained through the color separation achieved at the dichroic mirrors 62 and 63 in further detail, the optical axes of these different color light fluxes respectively enter the polarization splitter portions of the polarization beam splitter 64R, 64G and 64B with an angle of incidence of 45xc2x0. The light that has entered each polarization splitter portion undergoes polarization splitting and is separated into S-polarized light to be reflected at the polarization splitter portion and P-polarized light to be transmitted through the polarization splitter portion. The S-polarized light are allowed to enter the reflection type light valves 65R, 65G and 65B provided near the exit surfaces of the polarization beam splitters 64R, 64G and 64B provided in correspondence to the individual color light. The individual color light having been modulated and reflected at the reflection type light valves 65R, 65G and 65B re-enter the polarization splitter portions of the polarization beam splitters 64R, 64G and 64B respectively. The light fluxes having re-entered the polarization splitter portions undergo an analyzing and, as a result, the P-polarized light fluxes that are the modulated light fluxes are detected as transmitted light and are extracted. The analyzed light fluxes corresponding to the different colors then undergo a color composition at the cross dichroic prism 66. As explained above, the polarization beam splitters 64R, 64G and 64B are each constituted to function both as a polarization splitting optical system and as an analyzing optical system.
The polarization beam splitters 64R, 64G and 64B each assume a structure achieved by inserting a polarization splitter film between two isosceles right-triangular prisms and bonding them together, and they have a roughly square sectional shape.
The polarization beam splitters 64R, 64G and 64B provided in correspondence to the different colors of light are each formed in a cubic shape or a rectangular parallelopiped shape which is achieved by inserting a polarization splitter film between two isosceles right-triangular prisms with identical sectional shapes. In other words, the polarization beam splitters 64R, 64G and 64B may each be regarded as a block of optical glass. A problem arises when the three blocks are provided in correspondence to the different colors of light since the volumetric space occupied by the optical systems and the weight of the optical systems are bound to increase.
In addition, while the polarization beam splitters 64R, 64G and 64B fulfill a crucial function as analyzing optical systems as explained above, it is desirable to ensure that when the light that have been modulated while being reflected at the light valves 65R, 65G and 65B (linearly polarized light) are transmitted through transparent optical members (glass portions) constituting the polarization beam splitters 64R, 64G and 64B, they do not adversely affect the states of the polarization. Otherwise, the states of the polarization will change while the modulated to light fluxes are transmitted through the glass portions and, a result, modulated light different from the original modulated light will be detected, thereby reducing the contrast of the projected image.
While a glass prism material with a low photoelastic constant may be used to constitute the prisms to reduce the degree to which the polarization states change, the use of such a material which has a particularly large specific gravity among various optical glass materials will lead to an increase in the weight of the optical systems.
An object of the present invention is to provide a more compact and lightweight polarizing device and a more compact and lightweight projector which employees the polarizing device for polarization splitting and light analyzing.
In order to attain the above object, a polarizing device according to the present invention comprises: a first prism substantially formed in a triangular shape; a second prism substantially formed in a triangular shape and bonded to the first prism; a polarization splitter film provided at a bonding surface at which the first prism and the second prism are bonded to each other; and a shape of a section of the first prism being determined so as to allow an optical axis of light having entered through one surface of the first prism to enter the polarization splitter film with an angle of incidence smaller than 45xc2x0.
Another polarizing device according to the present invention comprises: a triangular first prism having a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a triangular second prism having a section substantially formed in a triangular shape having a first interior angle equal to the second interior angle and the third interior angle of the first prism; and a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and one surface of the second prism, which is one of two surfaces enclosing the first interior angle of the second prism, are bonded to each other, and a second surface and a third surface respectively faces opposite the second interior angle and the third interior angle of the first prism, an angle of incidence at the polarization splitter film of an optical axis of light having entered through the second surface is equal to the second interior angle and the third interior angle of the first prism, and the light reflected at the polarization splitter film exits through the third surface of the first prism.
Another polarizing device according to the present invention comprises: a first prism with a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a second prism with a section substantially formed in a triangular shape having at least one first interior angle set equal to the second interior angle and the third interior angle of the first prism which are acute angles; and a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and a first surface which is one of two surfaces enclosing the first interior angle of the second prism, are bonded to each other, and light is allowed to enter the second prism through a second surface which is one of the two surfaces enclosing the first interior angle of the second prism, and light transmitted through the polarization splitter film exits through a second surface of the first prism facing opposite the second interior angle.
A projector according to the present invention comprises: a color separation optical system that separates a light flux emitted by a light source into light fluxes corresponding to a plurality of colors; a plurality of light valves provided in correspondence to the plurality of colors of light fluxes respectively; a plurality of polarizing devices provided to achieve polarization splitting of the light fluxes corresponding to the plurality of colors having exited the color separation optical system, guide the light fluxes to the plurality of light valves and individually analyze the light fluxes corresponding to the plurality of colors having been modulated at the plurality of light valves; and a color composition optical system that composes the light fluxes corresponding to the plurality of colors having been analyzed at the plurality of the polarizing devices and having exited the plurality of polarizing devices, and each of the polarizing devices comprises: a first prism substantially formed in a triangular shape; a second prism substantially formed in a triangular shape and bonded to the first prism; a polarization splitter film provided at a bonding surface at which the first prism and the second prism are bonded to each other; and a shape of a section of the first prism being determined so as to allow an optical axis of light having entered through one surface of the first prism to enter the polarization splitter film with an angle of incidence smaller than 45xc2x0.
An optical apparatus according to the present invention comprises: a light valve; and a light analyzing device that analyzes light exiting the light valve, and the light analyzing device comprises: a first prism having a section substantially formed in a triangular shape; a second prism having a section substantially formed in a triangular shape and bonded to the first prism; a polarization splitter film provided between bonding surfaces of the first prism and the second prism; and a shape of a section of the first prism being determined so as to allow an optical axis of light having entered through one surface of the first prism from the light valve to enter the polarization splitter film with an angle of incidence smaller than 45xc2x0.
Another optical apparatus according to the present invention comprises: a light valve; and a light analyzing device that analyzes light exiting the light valve, and the light analyzing device comprises: a first prism with a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a second prism with a section substantially formed in a triangular shape having at least one first interior angle equal to the second interior angle and the third interior angle of the first prism which are acute angles; a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and a first surface which is one of two surfaces of the first surface and a second surface enclosing the first interior angle of the second prism, are bonded to each other; and a second surface and a third surface facing opposite the second interior angle and the third interior angle respectively at the first prism, and the light having exited the light valve being caused to enter the first prism through the second surface of the first prism.
In this optical apparatus, it is preferred that analyzed light in light which has exited the light valve and entered through the second surface of the first prism at the light analyzing device exits through the third surface of the first prism or the second surface of the second prism.
A projection type display apparatus according to the present invention comprises: a light valve; an optical device that guides light obtained by achieving polarization splitting on incident light to the light valve and analyzes light having exited the light valve; and a projection lens that projects the light analyzed by the optical device, and: the optical device comprises a first prism and a second prism both with a section substantially formed in a triangular shape and a polarization splitter film provided at a bonding surface between the first prism and the second prism; and an optical axis of the incident light having entered through one surface of the first prism, enters the polarization splitter film at an angle of incidence smaller than 45xc2x0 and reflected light or transmitted light achieved through the polarization splitter film is allowed to enter the light valve.
Another projection type display apparatus according to the present invention comprises: a light valve; an optical device that guides light obtained by achieving polarization splitting on incident light to the light valve and analyzes light having exited the light valve; and a projection lens that projects the light analyzed by the optical device, and the optical device comprises: a first prism with a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a second prism with a section substantially formed in a triangular shape having at least one first interior angle equal to the second interior angle and the third interior angle of the first prism which are acute angles; a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and a first surface which is one of two surfaces of the first surface and a second surface enclosing the first interior angle of the second prism, are bonded to each other; and a second surface and a third surface facing opposite the second interior angle and the third interior angle of the first prism respectively, the incident light being caused to enter the first prism through the second surface of the first prism, and reflected light obtained at the polarization splitter film being allowed to exit the first prism through the third surface of the first prism to enter the light valve.
Another projection type display apparatus according to the present invention comprises: a light valve; an optical device that guides light obtained by achieving polarization splitting on incident light to the light valve and analyzes light having exited the light valve; and a projection lens that projects the light analyzed by the optical device, and the optical device comprises; a first prism with a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a second prism with a section substantially formed in a triangular shape having at least one first interior angle equal to the second interior angle and the third interior angle which are acute angles at the first prism; a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and a first surface which is one of two surfaces enclosing the first interior angle of the second prism, are bonded to each other; and the incident light allowed to enter the second prism through a second surface which is one of the two surfaces enclosing the first interior angle of the second prism, and light having been transmitted through the polarization splitter film allowed to exit the first prism through a second surface of the first prism to enter the light valve.
A compound prism member according to the present invention comprises: a triangular first prism with a section substantially formed in an isosceles triangular shape having a first interior angle which is an obtuse angle and a second interior angle and a third interior angle which are acute angles equal to each other; a triangular second prism with a section substantially formed in a triangular shape having at least one first interior angle equal to the second interior angle and the third interior angle of the first prism which are acute angles; and a polarization splitter film provided at a bonding surface at which a first surface of the first prism facing opposite the first interior angle and a first surface which is one of two surfaces of the first surface and a second surface enclosing the first interior angle of the second prism, are bonded to each other.
Another projector according to the present invention comprises: a color separation optical system that separates a light flux emitted by a light source into light fluxes corresponding to a plurality of colors; a plurality of light valves provided in correspondence to the plurality of colors of light fluxes respectively; a plurality of polarizing devices provided to achieve polarization splitting of the light fluxes corresponding to the plurality of colors having exited the color separation optical system, guide the light fluxes to the plurality of light valves and individually analyze the light fluxes corresponding to the plurality of colors having been modulated at the plurality of light valves and then guided to the plurality of polarizing devices; and a color composition optical system that composes the light fluxes corresponding to the plurality of colors having been analyzed at the plurality of the polarizing devices and having exited the plurality of polarizing devices, and: the plurality of polarizing devices each includes a polarization splitter film through which one light flux emitted from the color separation optical system undergoes polarization splitting to be guided to one of the light valves and the one light flux having been modulated at the light valve and having been guided to the polarization splitter film is analyzed; and the polarization splitter films at the plurality of polarizing devices are formed so as to ensure that optical axes of light fluxes corresponding to the plurality of colors having been analyzed at the plurality of polarizing devices and having exited the plurality of polarizing devices enter the color composition optical system parallel to one another or perpendicular to one another and that the optical axes of the light fluxes corresponding to the plurality of colors exiting the color separation optical system enter the polarization splitter films at an angle of incidence smaller than 45xc2x0.